The present invention is directed toward the field of applying images to a medium such as paper. In particular, the invention relates to printers and methods of printing incorporating aspects of xerographic and ink jet printing technologies.
Among the technologies available for applying an image to a medium, such as paper, are xerography and direct marking. Common forms of direct marking include ink pen and ink jet marking technologies.
Xerographic printing typically uses a dry toner and produces on a print medium a clear, durable image. However, those familiar with xerography will also recognize that the hardware required for xerographically printing images, and particularly for printing images in multiple colors, may be somewhat complex.
In conventional xerography, electrostatic latent images are formed on a xerographic surface by first uniformally charging a charge retentive surface such as a photoreceptor. The charged area is selectively dissipated in accordance with a pattern of activating radiation corresponding to the original image. The selective dissipation of the charge leaves a latent charge pattern on the imaging surface corresponding to the areas not exposed by radiation. This charged pattern is made visible by developing it with toner. Such development includes passing the photoreceptor past one or more developer housings. Color xerographic printing commonly requires multiple developers, generally three color developers (yellow, cyan, and magenta) plus a black developer. The developed image is then fixed to the imaging surface, or is transferred to a receiving medium such as paper, to which it is fixed by suitable fusing techniques.
Direct marking technologies, and in particular ink jet printing, have emerged as printing alternatives that incorporate relatively simpler hardware requirements. However, images produced with the inks used in ink jet marking technologies, and particularly in thermal ink jet marking technologies, do not always exhibit the same high level of clarity or permanence as xerographically produced images.
In direct marking technologies, ink in the desired image is applied directly to the print medium. Various techniques of direct marking are well understood in the art. For example, the image may be applied by direct contact between a pen and the medium. Alternatively, ink jet recording techniques eject droplets of ink from a printhead onto the medium. Such ink jet techniques may include thermal ink jets, acoustic ink jet, piezo-electric ink jet printing, and others.
Ink jet recording devices eject ink onto a print medium such as paper in controlled patterns of closely spaced dots. To form color images, multiple groupings of ink jets are used, with each group being supplied with ink of a different color from an associated ink container.
Referring particularly to thermal ink jet printing systems, such systems use thermal energy selectively produced by resistors located in capillary filled ink channels near channel terminating nozzles or orifices to vaporize momentarily the ink, and form bubbles on demand. Each temporary bubble expels an ink droplet and propels it toward a recording medium. The printing system may be incorporated in either a carriage type printer or a page width type printer. A carriage type printer generally has a relatively small printhead containing the ink channels and nozzles. The printhead is usually attached to an ink supply container, and the combined printhead and container form a carriage assembly that is reciprocated to print one swath of information at a time on a stationary recording medium. After the swath is printed, the paper is stepped in a distance equal to the height of the printed swath, so that the next printed swath will be contiguous. In contrast, a page width printer has a stationary printhead having a length equal to or greater than the width of the medium. The medium is continually moved past the page width printhead in a direction normal to the printhead length at a constant speed during the printing process.
The present invention is a method and apparatus for printing an image onto a medium incorporating a novel combination of aspects of both xerographic and direct marking print technologies.
In accordance with the method of the present invention, toner is applied to an intermediate element such as a charge receptor to form a toner layer on the intermediate element. A first ink image is then deposited onto the toner layer on the intermediate surface. The ink image and the toner layer are then transferred onto a print medium, and the ink image and the toner layer are fixed onto the medium.
The apparatus of the present invention is a printer that includes an intermediate surface, a developer for applying a toner layer to the intermediate surface, and a direct marking element for applying a first ink image to the toner layer on the intermediate surface. The printer further includes a transfer element for transferring the first image and the toner layer from the intermediate surface to a print medium.